Load weight monitoring system for dump truck

ABSTRACT

The present invention enables a reliable radio communication between a plurality of dump trucks and loaders, improves operability, and can flexibly cope with movement of the dump truck during the loading operation. To this end, a loader selecting means (2) is provided for each dump truck, and a plurality of channels are provided for each dump truck controller (6) and each loader controller (35), the dump truck controller (6) inputs a loader selection signal from the loader selecting means (2), and selects, from a plurality of channels, a channel available for communicating with the loader controller (35) corresponding to the loader selection signal to transmit a load weight value, and the selected loader controller (35) receives the load weight value on the channel available for communications, and displays the received load weight value on a weight display means (32).

TECHNICAL FIELD

The present invention relates to a load weight monitoring system formonitoring the load weight of a dump vehicle (hereinafter, referred toas a dump truck) from a loading operation vehicle (hereinafter, referredto as a loader), and more particularly, to a load weight monitoringsystem for a dump truck for use in a system in which a plurality of dumptrucks and a plurality of loaders operate in cooperation.

BACKGROUND ART

In a field, such as a quarry, where a plurality of dump trucks andloaders are systematically operated within a relatively wide workingarea, they usually operate in cooperation with each other. For example,when a dump truck without a load enters the quarry and stops near anoperator-waiting loader, the loader loads stones, rocks, earth, and/orsand on a bed (hereinafter, referred to as a body) of the dump truck.After loading up to a maximum allowable load weight (hereinafter,referred to as a rated load weight), an operator of the loader sends asignal of load completion with a horn, etc., to an operator of the dumptruck, and waits for the next dump truck without a load to arrive. Theoperator of the dump truck carries the loaded stones, rocks, earth,sand, etc., to a predetermined earth dumping field to discharge them,and then returns to the quarry to repeat the above operating procedure.

In a field where dump trucks and loaders are thus systematicallyoperated, it is desirable to secure a maximum production by increasingthe driving efficiency of the dump trucks and loaders. Thus, it isnecessary to increase the amount that a dump truck carries at one time.

On the other hand, when the dump truck travels in a condition in whichthe rated load weight is exceeded, i.e., in a so-called overloadedcondition, the weight greatly influences the durability of each part ofthe vehicle such as the vehicle body, the wheel mounting portions, andthe suspension. For this reason, when traveling in an overloadedcondition, the dump truck must travel at a limited vehicle speedcorresponding to the overload amount, so the driving efficiency does notincrease very much.

For reasons as described above, in order to obtain the maximum loadweight that the dump truck can carry at one time, the operator of theloader has conventionally performed a loading operation while monitoringthe load weight so that the load weight approaches as close as possibleto the rated load weight of the dump truck. As an example of such a loadweight monitoring system, Japanese Unexamined Patent Publication No.6-82295 has been proposed. The load weight monitoring system includes acontroller for calculating the load weight, a load weight display fordisplaying the calculated load weight, and a transmitter fortransmitting the load weight as a signal, each provided on the dumptruck. In addition, in a driver's cab on the loader, a receiver forreceiving the above load weight signal and a display section fordisplaying the received load weight are provided.

The controller on the dump truck opens a communication link when theload weight of the dump truck changes by a predetermined weight value ormore due to a first loading, and thereafter keeps on transmitting theload weight signal, and disconnects the communication link when thetransmission shift lever is moved from neutral to a position other thanneutral. The receiver on the loader displays the received load weightsignal on the display section when the communication link is open, andswitches the weight display to another display when the communicationlink is disconnected. In this way, the operator on the loader can learnthe load weight by watching the display section, and makes a sign ofload compilation to the operator on the dump truck by means of a horn,etc., provided on the loader.

However, in the above load weight monitoring system, since the samesingle fixed frequency is used as the radio frequency on the dump truckand on the loader, interference often occurs when a plurality of dumptrucks and loaders operate simultaneously in cooperation with eachother. For this reason, communication links among other vehicles aredisconnected in order to avoid the interference, and opening of thecommunication links is deferred, so that dead time is produced. Inaddition, when a communication link is opened, it should be checked asto whether or not the desired loader is reliably connected to thecommunication link, so that a problem causing troublesome work isencountered.

In addition, since a current load weight value is displayed on thedisplay section on the loader, the loader operator must calculate theremaining weight needed to reach the rated load weight from the currentload weight value, and must consider how much should be loaded beforethe loading is completed. This is troublesome work for the loaderoperator, thus offering low operability. When judging a load completion,the loader operator makes a sign to the dump truck operator by soundinga horn, etc., on the loader, but the sound may be inaudible in ahigh-noise field environment. A voice radio can be separately used inplace of the horn to directly check between the operators, but it isexpensive, and a troublesome operation is required, such as tuning thevoice radio frequency on the dump truck to the voice radio frequency onthe respective loader.

In addition, the dump truck operator may decide to complete the loadingand start the dump truck before the load weight reaches the rated loadweight. To this end, in the load weight monitoring system, thecommunication links can be disconnected when the transmission shiftlever is moved, from neutral to a position other than neutral, upon astarting of the dump truck. However, due to the communication linkdisconnection, the monitoring system cannot cope with an operation suchthat the dump trucks and the loaders perform loading while alternatelyrepeating forward and reverse movements, i.e., a so-called cross loadingoperation. This is because the transmission shift lever is moved fromneutral to a position other than neutral upon a starting of the dumptruck while the cross loading operation is performed, so thecommunication links are disconnected. Therefore, since the latest loadweight cannot be displayed on the display section on the loader, theweight cannot be controlled in such a manner as to approach the ratedload weight.

SUMMARY OF THE INVENTION

The present invention has been made to solve the problems of the priorart, and its object is to provide a load weight monitoring system for adump truck which can reliably monitor, from a loader, the load weight ofa dump truck to achieve an improvement in operability for the operatorsfor the dump truck and the loader even if a plurality of dump trucks andloaders operate simultaneously in cooperation with each other, and whichcan flexibly cope with free movement of the dump trucks during theloading operation.

In a first aspect of a load weight monitoring system for monitoringsimultaneous loading operations of a plurality of dump trucks and aplurality of loaders according to the present invention, there isprovided: a load weight monitoring system for a dump truck including adump truck controller, provided for each of the plurality of dumptrucks; a loader controller, provided for each of the plurality ofloaders and available for communicating by radio with a dump truckcontroller; a weight detector, provided for each loader, to detect theload weight of a respective dump truck; and a weight display means,provided for each loader, to display the load weight through a dumptruck controller and a loader controller; the system comprising:

a loader selecting means, provided for each dump truck, to select anyone of the plurality of loaders; and a plurality of channels providedfor each dump truck controller and said each loader controller,

wherein the dump truck controller inputs a loader selection signal fromthe loader selecting means, selects from a plurality of channels of thedump truck controller a channel available for communications with theloader controller corresponding to the loader selection signal, andtransmits a load weight signal, and

wherein the selected loader controller receives the load weight signalon the channel available for communications, and displays the receivedload weight on the weight display means.

A remaining weight display means can be attached to each loadercontroller, and the loader controller preferably calculates thedifference between a rated load weight value, stored in advance in eachdump truck controller, and the actual load weight value, and can displaythe calculated difference on the remaining weight display means.

The system can further comprise a start permission input switch attachedto each loader controller, and a start permission reporting meansattached to each dump truck controller; the loader controller, wheninputting a dump truck start permission signal from the start permissioninput switch, can transmit the start permission signal to the dump truckcontroller on the channel available for communications; and the dumptruck controller, which has received the start permission signal, canreport a start permission signal to an operator by the start permissionreporting means.

A radio communication prohibition switch can be attached to each dumptruck controller, and the dump truck controller can prohibit thetransmission of an open request to the loader controller when a radiocommunication prohibition signal, inputted from the radio communicationprohibition switch, is set for communication prohibition, and cantransmit the load weight on the channel available for communicationswhen the radio communication prohibition signal is not set forcommunication prohibition.

A standby input switch can be attached to each loader controller, andthe loader controller can open a radio communication link with the dumptruck controller to receive the load weight signal on the channelavailable for communications when a standby signal, inputted from thestandby input switch, is set at standby, and cannot accept the requestfor opening the radio communication link from the dump truck controllerwhen the standby signal is not set at standby.

A communication anomaly reporting means can be attached to at least oneof each loader controller and each dump truck controller, so that whenan error of the received data or a communication anomaly such that ano-response condition occurs a predetermined number of times or more isjudged, each loader controller or each dump truck controller, to whichthe communication anomaly reporting means is attached, can report thecommunication anomaly to an operator by the communication anomalyreporting means.

A remaining weight display means and a communication link disconnectrequesting means can be attached to each dump truck controller, and thedump truck controller can calculate the difference between a rated loadweight value, stored in advance, and the actual load weight value,display the calculated difference on the remaining weight display means,and forcibly disconnect a radio link with each loader controller wheninputting a communication link disconnect request signal from thecommunication link disconnect requesting means.

The communication link disconnect requesting means can be comprised of atravel distance detector for detecting a travel distance of the dumptruck, and a communication link disconnect judging means for inputtingthe detected travel distance; and the communication link disconnectjudging means can output the communication link disconnect requestsignal to the dump truck controller when the detected travel distancebecomes equal to or exceeds a predetermined value.

According to the described construction of the first aspect, in the casewhere a plurality of dump trucks and loaders simultaneously operate incooperation, one of a plurality of channels is exclusively used as achannel for radio communication between a specific dump truck and thecorresponding loader. Thus, the signal for the load weight of the dumptruck can be transmitted to the loader without interference, and theload weight can be reliably monitored from the loader. In addition, bydisplaying on the loader the remaining weight value, the loader operatorcan easily decide how much more should be loaded. Thus, the operatordoes not have to make a troublesome calculation, thus offering highoperability.

In addition, when the loader operator judges a load completion, andoperates the start permission input switch, the start permission signalis directly transmitted to the dump truck by radio communication. On thedump truck, the start permission can be reported to the operator when astart permission signal is received. This allows a sign of a loadcompletion to be sent to the operator on the dump truck without beinginfluenced by field noise.

Further, by attaching the radio communication prohibition switch or thestandby input switch, a vehicle removed from the system can be broughtinto a condition where radio communication cannot be accomplished. Thatis, when a vehicle among the dump trucks and loaders in use is removedfrom the system, e.g., for maintenance, the standby input switch on theloader is set to "standby-off condition" and the radio communicationprohibition switch on the dump truck is set to "radio communicationprohibited condition". This can prevent radio interference withoutperforming a useless communication link opening with the other dumptrucks and loaders which are being used in the system. In addition, byattaching the communication anomaly reporting means, an occurrence ofthe radio communication anomaly can be reported to the operator by thecommunication anomaly reporting means. This can prevent thecommunication link from taking a long period of time to be opened, andprevent a display of the load weight from lagging behind the truetiming. Therefore, the operator can immediately cope with thecommunication anomaly, thus improving operability.

Still further, by attaching the remaining weight display means and thecommunication link disconnect requesting means to each dump truckcontroller, when the dump truck operator watches the display of theremaining load weight and decides that the loading can be completed, theoperator can move the dump truck to the earth dumping field withoutwaiting for a start permission signal for the dump truck from the loaderoperator. This can flexibly cope with free movement of the dump truck,such as a cross loading operation, during the loading operation. And,when the dump truck is moved by the decision of the operator,interference of the radio link can be better prevented when the usedradio link is disconnected. In addition, in the case where thecommunication link disconnect requesting means is comprised of thetravel distance detector and the communication link disconnectrequesting means, when the travel distance data of the dump truckbecomes equal to or exceeds a predetermined value, it can be judged thatthe dump truck is moving toward the earth dumping field such that theradio link can be disconnected. This can disconnect a uselesscommunication link, and prevent radio interference.

In a second aspect of a load weight monitoring system for monitoringloading operations of a dump truck and a loader, there is provided aload weight monitoring system for the dump truck including: a dump truckcontroller, provided on the dump truck; a loader controller, provided onthe loader and available for communicating by radio with the dump truckcontroller; a weight detector, provided on the dump truck to detect theload weight of the dump truck; and a weight display means, provided onthe loader to display the detected load weight through the dump truckcontroller and the loader controller; the system comprising:

a start permission input switch, provided on the loader, and acommunication link disconnect requesting means provided on the dumptruck,

wherein the loader controller, when inputting a dump truck startpermission signal from the start permission input switch, transmits thestart permission signal to the dump truck controller, and the dump truckcontroller forcibly disconnects a radio link with the loader controllerwhen receiving the start permission signal from the loader controller,or when inputting a communication link disconnect request signal fromthe communication link disconnect requesting means.

The communication link disconnect requesting means can be comprised of atravel distance detector for detecting the travel distance of the dumptruck, and a communication link disconnect judging means for inputtingthe detected travel distance, and the communication link disconnectjudging means can output the communication link disconnect requestsignal to the dump truck controller when the detected travel distancebecomes equal to or exceeds a predetermined value.

According to the described construction of the second aspect, even inthe case of one loader, the same actions as those of the first aspect ofa plurality of loaders can be obtained. Particularly, the function ofthe communication link disconnect requesting means to forciblydisconnect the communication link from the dump truck is effective evenin the case of one loader, and this can cope with a flexible loadingoperation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a functional block diagram of a dump truck side showing abasic construction of a first embodiment of the present invention;

FIG. 2 is a functional block diagram of a loader side showing a basicconstruction of the first embodiment;

FIG. 3 is a hardware block diagram of the dump truck side of the firstembodiment;

FIG. 4 is a hardware block diagram of the loader side of the firstembodiment;

FIGS. 5A, 5B, and 5C are drawings each showing the first half of acommunication control procedure of the load weight monitoring system ofthe first embodiment, in which FIG. 5A is a flowchart in a CPU 20;

FIG. 5B is an illustration showing transmitting/receiving data or acommunication control command between FIG. 5A and FIG. 5C; and

FIG. 5C is a flowchart in a CPU 50;

FIG. 6A is a flowchart of the procedure following FIG. 5A;

FIG. 6B is an illustration showing transmitting/receiving data or acommunication control command between FIG. 6A and FIG. 6C;

FIG. 6C is a flowchart of the procedure following FIG. 5C;

FIG. 7A is a flowchart of the procedure following FIG. 6A;

FIG. 7B is an illustration showing transmitting/receiving data or acommunication control command between FIG. 7A and FIG. 7C;

FIG. 7C is a flowchart of the procedure following FIG. 6C;

FIG. 8 is a functional block diagram of the dump truck side showing abasic construction of a second embodiment of the present invention;

FIG. 9 is a hardware block diagram of the dump truck side of the secondembodiment;

FIGS. 10A, 10B, and 10C are drawings each showing a communicationcontrol procedure of the load weight monitoring system of the secondembodiment, in which FIG. 10A is a flowchart of the procedure of the CPU20 which is performed following FIG. 6A;

FIG. 10B is an illustration showing transmitting/receiving data or acommunication control command between FIG. 10A and FIG. 10C;

FIG. 10C is a flowchart of the procedure of the CPU 50 which isperformed following FIG. 6C;

FIG. 11A is a flowchart of the procedure following FIG. 10A;

FIG. 11B is an illustration showing transmitting/receiving data or acommunication control command between FIG. 11A and FIG. 11C; and

FIG. 11C is a flowchart of the procedure following FIG. 10C.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiments of a load weight monitoring system for a dumptruck according to the present invention will now be described in detailwith reference to the attached drawings.

FIGS. 1 and 2 are functional block diagrams each showing a basicconstruction of a dump truck side and a loader side of a firstembodiment. First, with regard to the dump truck side, a controller 6 onthe dump truck (hereinafter, referred to as a dump truck controller 6)inputs a load weight signal from a weight detector 1, a loader selectionsignal from a loader selecting means 2, and a radio communicationprohibition signal from a radio communication prohibition switch 5. Inaddition, the dump truck controller 6 outputs a start permission signalto a start permission reporting means 3, and a communication anomalysignal to a communication anomaly reporting means 12. The dump truckcontroller 6 outputs the above-described inputted load weight signal anda communication control signal to a transmitter 15a, and inputs thestart permission signal, etc., from a receiver 15b. The transmitter 15aand the receiver 15b radio the load weight signal and the communicationcontrol signal through an antenna 15c to a transmitter-receiver 45 onthe loader.

Next, on the loader side, a controller 35 on the loader (hereinafter,referred to as a loader controller 35) communicates by radio with thetransmitter-receiver 15 on the dump truck side through an antenna 45cand the transmitter-receiver 45. The loader controller 35 inputs astandby signal from a standby input switch 31, and a start permissionsignal from a start permission input switch 33. In addition, the loadercontroller 35 outputs the load weight signal, inputted through thereceiver 45b, to a weight display means 32, and outputs to a remainingweight display means 41 the weight remaining until the rated weight isreached. The loader controller 35 outputs a communication anomaly signalto the communication anomaly reporting means 12.

Specific hardware block diagrams of the first embodiment are shown inFIGS. 3 and 4 in relation to FIGS. 1 and 2. The construction will bedescribed in detail with reference to FIGS. 3 and 4.

First, the dump truck side will be described. The weight detector 1detects the load weight, and is comprised of pressure sensors 1a and aweight calculation device 1b. The pressure sensors 1a detect thepressure in the extension chamber of a front wheel suspension cylinder,mounted between the body of the dump truck and the steering frontwheels, and in the extension chamber of a rear wheel suspensioncylinder, mounted between the body and the driving rear wheels, andoutput the pressure signals to the weight calculation device 1b. Theweight calculation device 1b inputs the pressure signals at the time ofloading earth, sand, etc., and calculates the load weight at that time,based on the difference from a previously inputted pressure signal atthe time of no load. The load weight signal is outputted to an interfacecircuit section 21.

Incidentally, the calculating function of the weight calculation device1b can be shared by the calculating function of a computer (hereinafter,a CPU 20) which constitutes the dump truck controller 6, and the weightcalculation device 1b can be included in the CPU 20.

The loader selecting means 2 selects an ID number of a loader, from aplurality of loaders, for loading the dump truck. In this embodiment, itis comprised of an alternative push-button switch. When a certain switchis pushed, other pushed buttons are mechanically reset and the newlypushed condition is mechanically held to output a loader selectionsignal corresponding to the newly pushed switch. For example, when asmany as five loaders are useable in a system, a quintuple alternativepush-button switch shown in FIG. 3 can be employed. Alternatively, theloader selecting means 2 can be a rotary selector switch, or a keyswitch type such that the ID number of the selected loader can bedirectly numerically inputted. The loader selection signal, outputted bythe loader selecting means 2, is outputted to the interface circuitsection 21.

The start permission reporting means 3 indicates a start permissionsignal to the operator by sound, voice, and/or display, and can becomprised of a buzzer 3a and a character display 3b. The buzzer 3a isprovided in the driver's cab so that the influence of noise is decreasedand the sound is audible to the operator. Alternatively, the means canbe comprised of a horn and a voice generator. The character display 3binputs a character display command from the CPU 20 through the interfacecircuit section 21 to display characters. For example, at the time of astart permission signal, the characters "START" as shown in FIG. 3 aredisplayed. In the case of the character display, since large amounts ofdata are usually inputted and/or outputted, the interface circuitsection 21 is comprised of a parallel or serial communication interface.In this embodiment, it is comprised of an 8-bit serial communicationinterface. In addition, as another example of display, switching oflight-up/light-out of a danger reporting light, a lamp, and an LEDdisplay can be employed.

The radio communication prohibition switch 5 prohibits an output of anopen request for a communication link from the dump truck side to theloader side, and is comprised of a push-button switch. That is, thearrangement is such that the switch is mechanically associated with theabove loader selection switch, and all the loader selection switches areswitched off when the radio communication prohibition switch 5 ispushed. Therefore, no loader selection signal is outputted at allthereafter, and the dump truck controller 6 does not output the openrequest for a radio communication link to the loader side. Incidentally,the radio communication prohibition switch 5 can be comprised of anormal switch which is not mechanically associated with the loaderselection switch, and the dump truck controller 6 can input a conditionof the radio communication prohibition switch to control the openrequest for the radio communication link.

The communication anomaly reporting means 12 reports the occurrence of acommunication anomaly to the dump truck operator by means of sound,voice and/or a display. The communication anomaly reporting means 12 canbe comprised of a buzzer, a horn, and/or a voice generator similar tothe start permission reporting means 3, or can be comprised of acharacter display, a danger reporting light, a lamp, and an LED display.

In this embodiment, the communication anomaly reporting means 12 doublesas the start permission reporting means 3. When the communicationanomaly occurs, the method of producing the sound differs from that usedat the time of the start permission signal. For example, the anomaly isreported by changing the interruption time of the sound. In addition, anerror code and a message representing the occurrence of thecommunication anomaly are displayed on the character display, and adisplay selection switch 10 for switching the contents of the display isincluded. The CPU 20 inputs a switching signal from the displayselection switch 10 through the interface circuit section 21, andswitches the contents of the display to the start permission display orthe communication anomaly display each time the switching signal is setON.

The dump truck controller 6 is comprised of a so-called microcomputersystem, and includes the CPU 20, the interface circuit sections 21 and22, and a bus 20a for inputting and outputting data and a CPU controlsignal to and from the outside, such as an external switch, a display,and a transmitter-receiver. In addition to a common storage section, aprocessing section, an execution control section, and an interruptservice section, the CPU 20 includes a ROM, in which a system programfor determining an execution procedure of the system is stored, and aRAM, for temporarily storing data, etc., during calculation andexecution.

Since the CPU 20 inputs and outputs signals and data to and from theperipheral switch, the display, and the transmitter-receiver, etc., theinterface circuit sections 21 and 22 adjust circuit connectingspecifications so that the CPU 20 can read and write the above signalsand data through the bus 20a. In this embodiment, although these arecollectively called interface circuit sections, the interface sectionwith the weight calculation device 1b and the character display 3b iscomprised of an input/output circuit of a so-called 8-bit serialcommunication, and the interface circuit section with thetransmitter-receiver 15 and each switch is comprised of a parallelinput/output circuit.

The transmitter 15a inputs the load weight signal and the radiocommunication control command from the CPU 20 through the interfacecircuit section 22, and transmits them by radio to the loader sidethrough the antenna 15c. In addition, the receiver 15b receives thestart permission signal and the radio communication control command byradio from the loader side through the antenna 15c, and outputs them tothe CPU 20 through the interface circuit section 22. Incidentally, afrequency for use in the radio communication is designated by the CPU20.

Next, the loader side will be described. The loader controller 35 iscomprised of a microcomputer similar to the dump truck controller 6, andincludes a CPU 50, a bus 50a, and the interface circuit sections 51 and52. The construction of the CPU 50 and the construction and functions ofthe bus 50a and the interface circuit sections 51 and 52 are the same asthose of the dump truck controller 6.

The receiver 45b of the transmitter-receiver 45 receives by radiothrough an antenna 45c the weight data and the radio communicationcontrol command transmitted from the transmitter 15a on the dump truckside, and outputs them to the CPU 50 through the interface circuitsection 52 and the bus 50a. In addition, the transmitter 45a inputs thestart permission signal and the radio communication control command fromthe CPU 50 through the bus 50a and the interface circuit section 52, andtransmits them by radio through the antenna 45c to the dump truck side.Incidentally, a frequency for use in the radio communication isdesignated by the CPU 50.

The standby input switch 31 selects whether or not the open request fora radio communication link from the dump truck side is accepted,sand iscomprised of an alternate selection switch. When the standby inputswitch 31 is selected in a standby condition, a standby signal isinputted to the CPU 50 through the interface circuit section 51 and thebus 50a.

The start permission input switch 33 is the switch operated by theloader operator when a start of the dump truck now loading is permitted,and is comprised of a push-button switch of a momentary type. When thestart permission input switch 33 is pushed, a start permission signal isinputted to the CPU 50 through the interface circuit section 51. Thestart permission signal is outputted to the transmitter 45a through theinterface circuit section 52. At the same time, the CPU 50 outputs ahorn driving signal to a horn driving relay 42b through the interfacecircuit section 51, whereby the horn driving relay 42b is actuated tosound a horn 42a.

The weight display means 32 and the remaining weight display means 41display a current load weight value and a value of weight remaininguntil the rated load weight value is reached, respectively. In thisembodiment, a character display is employed similar to the startpermission reporting means 3. In addition, since the weight displaymeans 32 doubles as the remaining weight display means 41, a displayselection switch 44 for switching the contents of the display isincluded. The display selection switch 44 is comprised of a switch of amomentary type. The CPU 50 inputs a switching signal from the displayselection switch 44 through the interface circuit section 51, andoutputs the load weight signal or the remaining weight signal throughthe interface circuit section 51 to the weight display means 32 eachtime the switching signal is set ON. Incidentally, the weight displaymeans 32 and the remaining weight display means 41 can be a numericalvalue display such as a 7-segment LED.

The communication anomaly reporting means 12 on the loader side is thesame as that on the above-described dump truck side and comprises thehorn 42a, the horn driving relay 42b, and the weight display means 32.The CPU 50 reports the communication anomaly by changing theinterruption time of the horn driving signal from that used at the timeof a start permission signal, as described above. In addition, the CPU50 outputs weight display data, remaining weight display data, and anerror message to the weight display means 32 each time the switchingsignal from the display selection switch 44 is set ON in the same manneras described above.

Next, an operation of the load weight monitoring system of thisembodiment according to the above construction will be described. Thisembodiment is the example which enables a radio communication betweeneach dump truck and each loader without interference in a system inwhich a plurality of dump trucks and a plurality of loaderssimultaneously operate in cooperation. Thus, in order to use a pluralityof radio communication frequencies, and at the same time, to use theplurality of radio frequencies effectively so as to flexibly cope withincreases and decreases in the number of the working vehicles used inthe system, a so-called multichannel access method is employed. That is,a plurality of data channels which can cope with the maximum number ofthe loaders expected to be used in the system are prepared, a free datachannel which is not currently used for communication is searched (aso-called carrier sense) from a plurality of data channels, and the dataand the communication control command are exchanged using the free datachannel.

Now, assume that a maximum of ten loaders are expected to be used in asystem, and only five loaders thereof are actually used. At this time,the maximum ten data channels which could be used in this system areprepared. In addition to the data channels, control channels forexchanging control information before starting communication with thedata channel are prepared. The number of the control channels can beone, but a plurality of channels is preferably prepared in order toreduce a waiting time at the time of opening the communication link. Forthe purpose of simplifying explanation, the number of the controlchannels is herein assumed to be one.

The CPU 20 of the dump truck controller 6, and the CPU 50 of the loadercontroller 35 form a main part of a radio communication control functionfor the load weight monitoring system of this embodiment. Processing ofthe CPU 20 and the CPU 50 will now be described with reference to FIGS.5A to 5C, FIGS. 6A to 6C, and FIGS. 7A to 7C. Incidentally, the contentsof processing executed by the CPU 20 and the CPU 50 are mainly describedbelow, and descriptions of the CPU 20 and the CPU 50 are suitablyomitted.

(Step 101) The CPU 20 inputs the loader selection signal from the loaderselecting switch 2 through the interface circuit section 21.

(Step 102) It is judged whether or not the above loader selection signalis ON. If ON, a procedure advances to step 103. If OFF, the procedurereturns to step 101 to repeat the above until the signal is judged to beON.

(Step 103) Next, free channels which are not currently used forcommunication are sequentially searched among a plurality of datachannels (10 channels in this embodiment) prepared in advance. Morespecifically, whether or not the data or a control signal iscommunicated is checked for a predetermined period of time through thereceiver 15b with the use of a data channel to be initially searched. Ifcommunicated, the data channel is judged to be in use. In thisembodiment, since the load weight signal is transmitted from the dumptruck side to the loader side for each predetermined period of timeduring the use of the data channel, the presence or absence of thecommunication is checked at least for the predetermined period of time.When the data channel is judged to be in use, the next data channel issimilarly checked. When a free channel is judged, the procedure advancesto step 104.

(Step 104) The ID number of the loader corresponding to the loaderselection signal, inputted from the loader selecting switch, is read outof a memory in the CPU 20. When the ID number is fixedly stored, thememory can be a ROM, while the memory can be a RAM when storing the IDnumber so as to be variable. When the control channel is not in use, theID number of the above-described loader, and the above-describedsearched free channel information (channel frequency information) aretransmitted with the use of the control signal through the transmitter15a. Thereafter, the procedure advances to step 105.

Incidentally, when there are a plurality of control channels, a controlchannel which is not in use in a plurality of channels is searched, andthe above loader ID number and the free data channel information aretransmitted with the use of the free control channel. In addition, amethod of searching for a free control channel can be the same as theabove-described method of searching for a free data channel.

In step 104, when the radio communication prohibition switch 5 ispushed, and all the switches of the loader selecting switch 2 are notpushed, all of the loader selection signals, inputted from the loaderselecting switch 2, are set to OFF. At this time, the frequencyinformation, of the above free data channel, and the loader ID numberare not transmitted.

On the other hand, the CPU 50 performs the following processing duringthe period of time.

(Step 201) The CPU 50 inputs a standby signal from the standby inputswitch 31 through the interface circuit section 51.

(Step 202) It is judged whether or not the above standby signal is ON.If ON, the procedure advances to step 203. If OFF, the procedure returnsto step 201 to repeat the above process until the signal is judged to beON.

(Step 203) The ID number of the loader and the free data channelinformation transmitted from the CPU 20 are received through thereceiver 45b with the use of the control channel.

(Step 204) It is judged whether or not the inputted loader ID number iscoincident with a private ID number. If they are coincident with eachother, the procedure advances to step 205. If they are not coincident,the procedure returns to step 203 to repeat the above until the arecoincident with each other.

(Step 205) The free data channel information inputted in step 203 isstored in the RAM. In addition, a "receive OK" signal is transmittedthrough the transmitter 45a with the use of the same control channel asthat described above. Thereafter, communication is performed on the datachannel.

In the CPU 20, the procedure advances to the following steps after step104.

(Step 105) The CPU 20 inputs data received through the receiver 15b withthe use of the same control channel as the control channel which hastransmitted the free data channel information in step 104.

(Step 106) It is judged whether or not the received data are the"receive OK" signal transmitted by the CPU 50. If "receive OK", theprocedure advances to step 107. If not, the procedure returns to step105 to repeat the above processing until the data becomes "receive OK".

Thereafter, communication is performed on the data channel.

(Step 107) It is judged whether or not the loader starts loading basedon the scale of the load weight signal inputted from the weightcalculation device 1b. For example, the current value of the load weightis compared with the load weight before the start of loading, and whenthe difference therebetween becomes equal to or exceeds a predeterminedvalue, a load starting is judged. As the load weight before a loadstarting, the load weight after earth removal, and the load weight atthe time of the latest stopping can be considered. When a load startingis judged, the procedure advances to step 108. If not, the procedurewaits until a load starting is judged.

(Step 108) The frequency information of the above free data channel isoutputted to the transmitter 15a and the receiver 15b so that thecommunication frequency of the transmitter 15a and the receiver 15b isfixed to the communication frequency of the free data channel searchedin step 103.

(Step 206) The CPU 50 also outputs the frequency information of the freedata channel to the transmitter 45a and the receiver 45b so that thecommunication frequency of the transmitter 45a and the receiver 45b isfixed to the communication frequency corresponding to the free datachannel stored in step 205.

(Step 109) The private ID number, stored in the memory in advance, andthe rated load weight value data are read out. Incidentally, the privateID number can be set by, for example, an ID number setting switchmounted on a substrate provided in the dump truck controller 6. In thiscase, the CPU 20 can input the set data of the above ID number settingswitch through the interface circuit, and can read the rated load weightdata corresponding to the ID number from a predetermined address in thememory.

(Step 110) The ID number of the corresponding loader, the private IDnumber, and the rated load weight data are transmitted on the above freedata channel through the transmitter 15a.

(Step 207) The CPU 50 inputs the ID number of the loader, the private IDnumber on the dump truck side, and the rated load weight signal from thefree data channel through the receiver 45b. After checking that theinputted ID number of the loader is coincident with the private IDnumber, the data are stored in predetermined addresses of the RAM.

(Step 208) The CPU 50 transmits the "receive OK" signal through thetransmitter 45a.

(Step 111) The CPU 20 inputs the data received through the receiver 15b,and judges whether or not the data are the "receive OK" signal. If the"receive OK" signal, the procedure advances to step 112. If not, theprocedure returns to step 110 to repeat the processing.

(Step 112) The CPU 20 transmits an "ACK signal" through the transmitter15a. The "ACK" signal is the verification signal for verifying to eachother whether or not the communication is being normally done, and isthe code meaning "acknowledge". In this condition, the communicationlink is opened, and thereafter the procedure advances to step 113.

(Step 209) The CPU 50 inputs the data received through the receiver 45b,and judges whether or not the data are the "ACK signal". If the "ACK"signal, the procedure advances to step 210. If not, the procedurereturns to step 209 to repeat the processing, and to wait until the"ACK" signal is inputted.

(Step 210) In this condition, the communication link is opened. The CPU50 transmits a "load weight data request" signal through the transmitter45a. Thereafter, the procedure advances to step 211.

(Step 113) The CPU 20 inputs the received data, and judges whether ornot the data are a "load weight data request" signal. If the "loadweight data request" signal, the procedure advances to step 114. If not,the procedure returns to step 113 to repeat the processing, and to waituntil the "load weight data request" signal is inputted.

(Step 114) The CPU 20 inputs a current load weight value from the weightcalculation device 1b through the interface circuit section 21.

(Step 115) The inputted current load weight value is transmitted throughthe transmitter 15a. Thereafter, the procedure advances to step 116.

(Step 211) The CPU 50 inputs the current load weight value through thereceiver 45b.

(Step 212) A remaining weight value is calculated from the inputtedcurrent load weight value and the rated load weight value, stored in theabove-described RAM memory, based on the expression "remaining weightvalue=rated load weight value-current load weight value". The remainingweight value and the current load weight value are outputted to theweight display means 32 to be displayed thereon. In this embodiment, asdescribed above, the condition of the display selection switch 44 isinputted, and the contents of the display are switched each time theswitch is ON, thereby outputting the remaining load weight value or thecurrent load weight value.

(Step 213) The condition of the start permission input switch 33 isinputted to judge whether or not the start permission signal is ON. Ifthe start permission signal is ON, the procedure advances to step 214.If not, the procedure returns to step 211 to repeat the aboveprocessing.

(Step 214) A "start permission command" is transmitted through thetransmitter 45a. Thereafter, the procedure advances to step 215.

(Step 116) The CPU 20 judges whether or not the data inputted throughthe receiver 15b are the "start permission command". If the "startpermission command", the procedure advances to step 118. If not, theprocedure advances to step 117.

(Step 117) It is judged whether or not a predetermined period of timehas elapsed since the load weight signal was outputted in step 115. Ifthe predetermined period of time has elapsed, the procedure returns tostep 113, whereby the transmittance of the latest load weight signal isrepeated for each predetermined period of time. In addition, if thepredetermined period of time has not elapsed, the procedure returns tostep 116, whereby the procedure waits for the inputting of the "startpermission command".

(Step 118) The "ACK" signal is transmitted through the transmitter 15a.Thereafter, the procedure advances to step 119.

(Step 215) The CPU 50 judges whether or not the data inputted throughthe receiver 45b are the "ACK" signal. If the "ACK" signal, theprocedure advances to step 216. If not, the procedure returns to step215 to wait for the "ACK" signal.

(Step 216) In this step, a communication link disconnection processingis performed. That is, a reset command of the previously used datachannel information is outputted to the transmitter 45a and the receiver45b, whereby the used data channel is opened for communications betweenother vehicles.

(Step 217) The start permission horn 42a is actuated, through the startpermission horn driving relay 42b, to sound a start permission signal.In addition, a start permission message, etc., are displayed on theweight display means 32.

(Step 218) After performing the communication link disconnect processingin step 216, a lapse of a predetermined period of time is awaited. Afterthe lapse of the predetermined period of time, the procedure returns tostep 210 of the initial processing to wait for the link open requestfrom the dump truck side.

(Step 119) The CPU 20 performs a communication link disconnectionprocessing on the dump truck side in the same manner as that on theloader side. That is, a reset command of the previously used datachannel information is outputted to the transmitter 15a and the receiver15b, whereby the used data channel is opened for communications betweenother vehicles.

(Step 120) An actuation signal is outputted to the start permissionbuzzer to sound the start permission signal, and the start permissionmessage, etc., are displayed on the display of the start permissionreporting means 3. Thereafter, the procedure returns to the step 101 ofthe initial processing.

The above is the communication control procedure of the firstembodiment. Incidentally, although it is not illustrated, the presenceor absence of a communication anomaly is checked when receiving data andthe control signal. In this embodiment, a communication anomaly isdetected by the following two methods. The first one is a parity checkof the data which is commonly performed. When an error is detected inchecking a parity of the received data and the control signal, a "NACK"(No ACK) signal is transmitted to the opposite side to output are-sending request. When the same error is continuously detected apredetermined number of times or more, it is judged as a communicationanomaly.

The second one is a checking of the presence or absence of a responsewhether or not each transmitted data and control signal are received bythe opposite side. When there is no response to the transmittance of thedata and the control signal from the opposite side after the lapse of apredetermined period of time, for example, when the "ACK" signal and the"NACK" signal do not return, the data and the control signal aretransmitted again. When such a non-response condition continuouslyoccurs a predetermined number of times or more, it is also judged as acommunication anomaly. At the time of a communication anomaly, the CPUs20 and 50 can report it to the operator by means of each communicationanomaly reporting means 12, whereby the reliability of communication canbe improved, and the operator can easily learn of the occurrence of thecommunication anomaly.

As described in this embodiment, since a plurality of channels areprepared, and different data channels are exclusively used incommunication between a respective dump truck controller 6 and arespective loader controller 35, there is no waiting time at the time ofcommunication link opening, and radio interference is eliminated.Incidentally, as a method of using a plurality of data channels, thereis a method other than the multichannel access method of thisembodiment. For example, the channels to be used in thetransmitter-receiver of each loader are fixed to the channels differentfrom each other. Then, the dump truck controller 6 performscommunication in accordance with the channel corresponding to the loaderselected by the loader selecting means 2. By this communication method,the effect of the present invention does not change.

In addition, since the value, of weight remaining until the rated loadweight value is reached, is displayed on the loader side, the loaderoperator can watch the display and easily decide how much more should beloaded. In this embodiment, although the rated load weight value istransmitted from the dump truck side to the loader side and theremaining weight value is calculated and displayed on the loader sidebased on the rated load weight value, the remaining weight value can befirst calculated on the dump truck side, and then transmitted to theloader side. In this case, the remaining weight value can be transmittedtogether with the current value of the load weight, and the remainingweight value can be transmitted when a request command for the remainingweight is received from the loader side.

When the operator on the loader side judges the loading to be near therated load weight value, the operator pushes the start permission inputswitch, thereby directly transmitting the start permission signal to thedump truck side by radio communication. On the dump truck side, uponreceipt of the start permission signal, a sign can be made to theoperator by means of a start permission sound and/or a start permissiondisplay.

In the case of removing the dump truck or the loader from use in thesystem, when the removed vehicle is the dump truck, the radiocommunication prohibition switch is kept in a radio communicationprohibition state, while the standby input switch is kept in astandby-off state when the removed vehicle is the loader. By this, arequest for opening the communication link is not made from the dumptruck side, and the loader side does not accept the request for openingthe communication link from the dump truck side. As a consequence, auseless link is not opened, so that radio interference with unusedvehicles can be prevented.

When the dump truck controller 6 or the loader controller 35 detects thecommunication anomaly, the occurrence of the communication anomaly canbe reported to the operator by means of each communication anomalyreporting means. Thus, the operator can immediately cope with theanomaly treatment, and a communication response waiting time at the timeof the occurrence of the communication anomaly is shortened, thusimproving operability.

Next, a second embodiment according to the present invention will bedescribed.

Referring to FIG. 8, the components are the same as those of the firstembodiment except for a communication link disconnect requesting means 7and a remaining weight display means 11 on the dump truck side. Theremaining weight display means 11 displays a value of the weightremaining until the rated load weight value is reached, similar to theremaining weight display means 41 (see FIG. 2) on the loader side, andinputs display data from the dump truck controller 6.

The communication link disconnect requesting means 7 is comprised of atravel distance detecting means 8 and a communication link disconnectjudging means 9. The travel distance detecting means 8 comprises a pulsegenerator 8a, which is fixed to a driving axle shaft of the dump truckfor outputting a pulse signal train wherein the number of pulses isproportional to the number of rotations of the driving wheel; a countingmeans, for inputting the pulse signal train, outputted from the pulsegenerator 8a, to count the number of pulses; and a travel distancecalculation means 8c, for calculating and outputting travel distancebased on the integrated value of the counted value. The communicationlink disconnect judging means 9 judges whether or not the communicationlink is disconnected based on the travel distance outputted from thetravel distance calculation means 8c. When it is judged that thecommunication link should be disconnected, a communication linkdisconnection request signal is outputted to the dump truck controller6. The remaining weight display means 11 also employs the characterdisplay in this embodiment, which also doubles as the character display3b of the start permission reporting means 3, as shown in FIG. 9.

In addition, since all of the processing of the counting means 8b, thetravel distance calculation means 8c, and the communication linkdisconnect judging means 9 can be performed by a microcomputer, theseprocessings are realized with the use of the CPU 20 of the dump truckcontroller 6. This allows the pulse signal train, outputted from thepulse generator 8a, to be directly inputted to the CPU 20 through theinterface circuit section 21.

The communication control procedure in this embodiment is a flow suchthat a few procedures are added to FIGS. 7A to 7C of the firstembodiment, and it will be described mainly with reference to FIGS. 10Ato 10C and FIGS. 11A to 11C.

(Step 151) After the CPU 20 has inputted the load weight data requestcommand in step 113, the procedure advances to this step to judgewhether or not the dump truck is in a stopped condition. If in thestopped condition, the procedure advances to the above-described step114. If not in the stopped condition, the procedure advances to step152. The stopped condition is judged when a condition, where no pulsetrain signal is outputted from the pulse generator 8a, continues for apredetermined period of time or longer.

(Step 152) After a load starting has been judged in step 106, the pulsesignals, outputted from the pulse generator 8a, are counted; and thetravel distance is calculated based on the integrated value thereof.Then, it is judged whether or not the travel distance becomes apredetermined value or longer. If the distance becomes the predeterminedvalue or longer, the procedure advances to step 153. If not, theprocedure returns to step 151 to repeat the above.

(Step 153) A "link disconnect request command" is transmitted throughthe transmitter 15a. And, the above-described link disconnect processingis performed similarly, whereby the used data channel is opened forcommunications between other working vehicles.

(Step 251) The CPU 50 judges whether or not the data received throughthe receiver 45b are the "link disconnect request command". If the "linkdisconnect request command", the procedure advances to step 252. If not,the procedure advances to the above-described step 211.

(Step 252) The above-described link disconnect processing is performedsimilarly, whereby the used data channel is opened for communicationsbetween other working vehicles. Then, the procedure advances to theabove-described step 218, and the subsequent flow is the same as thatdescribed above.

Incidentally, after the load weight signal has been inputted in step 114and step 115, and the load weight signal has been transmitted by radioas the current load weight value, the procedure advances to step 161.

(Step 161) The rated load weight value, stored in a predeterminedaddress in the RAM memory, is read; and a remaining weight value iscalculated from the rated load weight value and the above current loadweight value based on the expression "remaining weight value=rated loadweight value-current load weight value". The remaining load weight valueis outputted to the remaining weight display means 11 to be displayedthereon. Thereafter, the procedure advances to the above-described step116.

As described above, the remaining load weight value is calculated anddisplayed on the remaining load weight display means in step 161, sothat the operator on the dump truck side can easily check the remainingweight without calculation. When the operator watches the display anddecides a load completion, the dump truck can be started. In addition,when the travel distance becomes a predetermined value or longer in step151 and step 152, it is judged that the dump truck is going toward aearth dumping field, so the communication link is disconnected andopened for other vehicles.

Further, besides the judgment by the travel distance, the dump truckoperator can perform a switch operation to request the communicationlink disconnection. In this case, the link disconnect request switch isprovided, and a link disconnect request signal from the switch isinputted to the dump truck controller 6, The CPU 20 judges whether ornot the link disconnect request signal is ON in the step correspondingto step 152. If ON, the procedure can advance to step 153. If not, theprocedure returns to step 151 to repeat step 151 and step 152.

Still further, although an example is described in which the remainingweight display means 11 and the link disconnect requesting means 7 areprovided on the dump truck side, and the communication link isdisconnected by the link disconnect requesting means 7 when the dumptruck operator watches the remaining weight display means 11 and decidesa load completion, it is not limited to the system of a plurality ofdump trucks and loaders. That is, it is effective in a system in which aplurality of dump trucks and one loader, or one dump truck and oneloader operate in cooperation. This increases judgment factors for theoperators on the dump truck side and on the loader side, respectively,so that the system can be flexibly operated.

According to the present invention as described above in detail, theload weight of the dump truck can be reliably monitored from the loaderwithout the interference of radio communication between the specificdump truck and loader even if a plurality of dump trucks and a pluralityof loaders operate in cooperation. In addition, the operator on theloader side can, without calculation, easily check the weight remaininguntil the rated load weight value is reached. When the operator on theloader side judges a load completion, by operating the start permissioninput switch, the start permission signal is directly transmitted to thedump truck side by radio communication, and a sign can be made to thedump truck operator by a start permission sound and display, wherebyoperability for the operators is improved.

Further, the dump truck or the loader removed from the system does notopen a useless link with the other dump trucks and loaders which arebeing used in the system, and radio interference is eliminated. Inaddition, at the time of an occurrence of a radio communication anomaly,the operator can immediately cope with the communication anomalytreatment. And, it becomes possible to cope with movement of the dumptruck during the loading operation, such as a cross loading operation,and to cope with a disconnection of the communication link in moving thedump truck during the loading operation to the earth dumping field dueto the judgment of the dump truck operator. These enable a flexibleoperation of the system.

INDUSTRIAL APPLICABILITY

The present invention is useful as a load weight monitoring system whichcan reliably transmit, without interference when transmitting by radio,the load weight of each dump truck to a corresponding loader, andimprove the operability for operators during a loading operation, andwhich can flexibly cope with free movement of the dump truck during theloading operation.

We claim:
 1. A load weight monitoring system for monitoring loadingoperations of a plurality of dump trucks and a plurality of loaders,said system comprising:a plurality of dump truck controllers, each dumptruck controller being for association with a respective one of theplurality of dump trucks; a plurality of loader controllers, each loadercontroller being for association with a respective one of the pluralityof loaders, each loader controller being available for communications byradio with an associated dump truck controller; a plurality of weightdetectors, each weight detector being for association with a respectiveloader to detect a load weight of an associated dump truck; a pluralityof weight display means, each weight display means being for associationwith a respective loader to display a detected load weight through anassociated dump truck controller and an associated loader controller; aplurality of loader selecting means, each loader selecting means beingfor association with a respective dump truck, for selecting from saidplurality of loaders a particular loader to be associated with therespective dump truck; and each said dump truck controller and eachloader controller being provided with a plurality of channels; wherein adump truck controller inputs a loader selection signal from a loaderselecting means, selects from a plurality of channels of that dump truckcontroller a channel available for communications between that dumptruck controller and a loader controller corresponding to said loaderselection signal, and transmits a load weight signal; and wherein aselected particular loader controller receives said load weight signalon said channel available for communications between the selectedparticular loader controller and the associated dump truck controller,and displays the received load weight signal on an associated weightdisplay means.
 2. A load weight monitoring system in accordance withclaim 1, further comprising:a plurality of dump truck start permissioninput switches, each dump truck start permission input switch beingassociated with a respective loader controller; a plurality of startpermission reporting means, each start permission reporting means beingassociated with a respective dump truck controller; wherein a loadercontroller, when inputting a dump truck start permission signal from adump truck start permission input switch, transmits a dump truck startpermission signal to an associated dump truck controller on the channelavailable for communications between the respective loader controllerand the associated dump truck controller; and wherein a dump truckcontroller, which has received a dump truck start permission signal,reports a start permission to an operator on that dump truck via therespective start permission reporting means.
 3. A load weight monitoringsystem in accordance with claim 1, further comprising:a plurality ofradio communication prohibition switches, each radio communicationprohibition switch being associated with a respective dump truckcontroller; and wherein a dump truck controller prohibits transmissionof an open request to an associated loader controller when a radiocommunication prohibition signal, inputted from an associated radiocommunication prohibition switch is set for communication prohibition,and transmits a load weight signal on said channel available forcommunications when said radio communication prohibition signal is notset for communication prohibition.
 4. A load weight monitoring system inaccordance with claim 1, further comprising:a plurality of standby inputswitches, each standby input switch being associated with a respectiveloader controller; and wherein a loader controller opens a radiocommunication link with an associated dump truck controller to receive aload weight signal on said channel available for communications when astandby signal, inputted from an associated standby input switch, is setat standby, and does not accept a request for opening said radiocommunication link from an associated dump truck controller when saidstandby signal is not set at standby.
 5. A load weight monitoring systemin accordance with claim 1, further comprising:a plurality ofcommunication anomaly reporting means, each communication anomalyreporting means being associated with at least one of a loadercontroller and an associated dump truck controller; and wherein when acommunication anomaly occurs, a controller, to which a communicationanomaly reporting means is attached, reports said communication anomalyto an operator by an associated communication anomaly reporting means.6. A load weight monitoring system in accordance with claim 1, furthercomprising:a plurality of remaining weight display means and a pluralityof link disconnect requesting means, each remaining weight display meansand each link disconnect requesting means being associated with arespective dump truck controller; and wherein each dump truck controllercalculates a difference between a rated load weight value, stored inadvance, and a respective load weight signal, displays the calculateddifference on an associated remaining weight display means, and forciblydisconnects a radio link with an associated loader controller wheninputting a link disconnect request signal from an associated linkdisconnect requesting means.
 7. A load weight monitoring system inaccordance with claim 6, wherein each link disconnect requesting meanscomprises a travel distance detector for detecting a travel distance ofan associated dump truck, and a link disconnect judging means forinputting a detected travel distance and for outputting a linkdisconnect request signal to an associated dump truck controller whensaid detected travel distance becomes equal to or exceeds apredetermined value.
 8. A load weight monitoring system in accordancewith claim 1, further comprising:a plurality of remaining weight displaymeans, each remaining weight display means being attached to arespective loader controller; and wherein said each loader controllercalculates a difference between a rated load weight value, stored inadvance in an associated dump truck controller, and said load weightsignal, and displays the calculated difference on an associatedremaining weight display means.
 9. A load weight monitoring system inaccordance with claim 8, further comprising:a plurality of startpermission input switches, each start permission input switch beingattached to a respective loader controller; and a plurality of startpermission reporting means, each start permission reporting means beingattached to a respective dump truck controller; wherein a loadercontroller, when inputting a dump truck start permission signal from anassociated start permission input switch, transmits a start permissionsignal to an associated dump truck controller on said channel availablefor communications; and wherein a dump truck controller, which hasreceived a start permission signal, reports a start permission to anoperator by an associated start permission reporting means.
 10. A loadweight monitoring system in accordance with claim 8, furthercomprising:a plurality of radio communication prohibition switches, eachradio communication prohibition switch being attached to a respectivedump truck controller; and wherein a dump truck controller prohibitstransmission of an open request to an associated loader controller whena radio communication prohibition signal, inputted from an associatedradio communication prohibition switch, is set at communicationprohibition, and transmits a load weight signal on said channelavailable for communications when said radio communication prohibitionsignal is not set at communication prohibition.
 11. A load weightmonitoring system in accordance with claim 8, further comprising:aplurality of standby input switches, each standby input switch beingattached to a respective loader controller; and wherein a loadercontroller opens a radio communication link with an associated dumptruck controller to receive said load weight signal on said channelavailable for communications when a standby signal inputted, from anassociated standby input switch, is set at standby, and does not accepta request for opening said radio communication link from an associateddump truck controller when said standby signal is not set at standby.12. A load weight monitoring system in accordance with claim 8, furthercomprising:a plurality of communication anomaly reporting means, eachcommunication anomaly reporting means being attached to either of aloader controller and a dump truck controller; and wherein, when acommunication anomaly is judged, a controller, to which a communicationanomaly reporting means is attached, reports the communication anomalyto an operator by an associated communication anomaly reporting means.13. A load weight monitoring system for a dump truck, said systemcomprising:a dump truck controller, provided for a dump truck; a loadercontroller, provided for a loader and available for communicating byradio with said dump truck controller; a weight detector, provided forsaid dump truck, to detect a load weight of said dump truck; and aweight display means, provided for said loader, to display said loadweight through said dump controller and said loader controller and formonitoring loading operations of said dump truck and said loader;wherein said loader is provided with a start permission input switch;wherein said loader controller, when inputting a dump truck startpermission signal from said start permission input switch, transmitssaid start permission signal to said dump truck controller; and whereinsaid dump truck controller forcibly disconnects a radio link with saidloader controller when receiving said start permission signal from saidloader controller.
 14. A load weight monitor system for a dump truck,said system comprising:a dump truck controller, provided for associationwith a dump truck; a loader controller, provided for association with aloader and available for communicating by radio with said dumpcontroller; a weight detector, provided for association with said dumptruck to detect a load weight of said dump truck; a weight displaymeans, provided for association with said loader, to display said loadweight through said dump truck controller and said loader controller,and for monitoring loading operations of said dump truck and saidloader; a travel distance detector, provided for association with saiddump truck, for detecting a travel distance of said dump truck; and alink disconnect judging means for inputting said detected traveldistance, wherein said link disconnect judging means outputs a linkdisconnect request signal to said dump truck controller when thedetected travel distance, after the start of a loading operation,becomes equal to or exceeds a predetermined value; and wherein said dumptruck controller, which has inputted said link disconnect requestsignal, forcibly disconnects a radio link with said loader controller.